Cardiac Binocular Rivalry Task.
(a) As in a typical binocular rivalry paradigm, incongruent gratings were presented to the left and right eyes, causing the subjects’ percept to alternate between the competing images. Each time the perceptually dominant image switched, subjects indicated so with a button press, and the durations of dominance were recorded. (b) The width of the bars in the grating would “pulse,” one in-phase and one anti-phase to the period of maximal blood pressure and thus maximal aortic baroreceptor activity following ejection of blood from the heart. (c) An example circular histogram of the cardiac phases/angles at which grating pulses peak over a full 10-minute block, as recorded from an actual subject. Angles are scaled such that the R-peak is always at π radians and the offset of the T-wave is at 0 radians, thus the lower half of the circle is cardiac systole and the upper half is diastole.